Transfer medium and method of making same



Match 9, 1937.

w. P. COHOE 2,072,943 I TRANSFER MEDIUM AND METHOD OF MAKING sum -Filed Nov. 30, 1935 INVENTOR Wallace Pa Patented Mar. 9, 1937 UNITED STAT TRANSFER MEDIUM AND ma'rnon or mum:

GSAME Wallace Patten Cohoe, New York, N. Y., assignol'; I by mesne assignments, to Underwood Elliott Fisher Company, New York, N. 'Y., a corporation of Delaware Application November 30, 1935, Serial No. 52,282

Claims.

This invention relates to a transfer medium and to a method of manufacturing the same. More particularly it relates to carbon webs or sheets, such as are extensively used for manifold- 5 ing in typewriters and various other business machines, and to an improved method of manufacturing such webs or sheets to provide the advantages hereinafter set forth.

Such webs and sheets are commonly made of a paper base faced with a transfer coating composition of comminuted carbon, coloring ingredient, camauba wax and petroleum jelly. According to the particular use in view they are made of varying weights of paper stock and varying degrees of hardness of the transfer material used' as a coating and each variation may have special applicability to some particular field of use and be in a measure unsuited to other uses. Each variation presents its own particular problems of manufacture but substantially all of them are subject to the common objection that under certain atmospheric conditions they tend tocurl from the edges in the direction of the transfer facing and under some conditions curl into a roll making the use of the same diflicult or in some instances impossible.

Another objection to transfer sheets now largely in commercial use is that owing to the smooth surface of the uncoated back of the paper, there is difliculty in obtaining and maintaining good alinement and registration of the components of the manifolding set because of the tendency of the interleaved transfer sheets to slip from position.

It is anobject of the present invention to remove these objections and provide a transfer sheet that will be substantially non-curling in character and both front and back surfaces of which are treated to prevent the tendency to slip from registered position. Other objects will appear as the description of this invention proceeds.

The reason for the curling tendency of transfer sheets is defined as due to unequal expansions 45 between the paper base or body of the sheet and its wax and carbon facing. The paper which is a felted mass of hydrated cellulose fibres has a hydroscopic characteristic whereas the wax and carbon coating at the face of the paper is comparatively impervious to atmospheric moisture changes. At times of high humidity the paper base will take up moisture from the atmosphere and'expand and the relative difference in expansion between the base and the coating brings 55 about the well-known result of curling in analogy to that so clearly apparent in bimetal thermostatic devices.

Curling of transfer also, to some extent,

sheets appears to be caused, from the uneven stresses set up in the facing of the paperwhen the transfer coating is applied in molten form and solidified. There is some impregnation by the molten wax composition of a substratum of the paper and the contraction of the facing of the paper attendant upon the solidification of the coating sets up stresses which are retained for some period of time until a natural rearrangement takes place which in a measure relieves the initial stresses.

It is believed, however, that whatever amount of seasoning time is given to the coating paper there always remains some stresses in the coating which have a tendency to distort to some extent the edges of the paper. Apparently there is always a tendency of the coating to remain stationary or to contract unless, of course, the paper is subjected to considerable heat. with these tendencies present in the transfer coating, whatever moisture is taken up by the paper base tends to cause curling of the sheet.

Sheets or webs treated witha facing of coating material, have heretofore been coated on their reverse or rear surfaces with compositions or solutions of various kinds. Such reverse coatings have been applied with the end in view of increasing the resistance of the paper to the blows of the type, that is, to toughen it or give it mechanical reenforcement purely. Papers having wax coated back surfaces have found some small sale commercially but have not attained any large measure of popularity because of their failure to satisfactorily meet the range of manifolding requirements. So far as is known, no such reversecoated paper has been made by which as good manifolding can be obtained under all conditions as with an ordinary carbon sheet untreated at the back surface. 'In the useofsuch sheets, the writes of the first copies will lack the desirable sharpness and if a large number of copies are to be produced simultaneously, those following the first two or three are illegible.

By the present invention a transfer sheet is produced which is substantially non-curling at all room temperatures, which has characteristics of durability. and longevity and in which there. is nosacrifice in sharpnessof write or legibility of all copies of the manifolding set and in which, as a matter of fact, it has been observed by comparison that the first writes in the manifolding set have sharpness superior to the first writes of .a set employing unbacked sheets.

of making atransfer sheet according to this invention.

Figure 2 is a similar view illustrating a subsequent step in the method and illustrative of the completed product.

The first part of the method which. is employed in carrying out the present invention diflers in no material respect from the conventional mannerof making a carbon-faced web according to known practice. A paper web is runfrom a roll through the feed rollers of a conventional coating machine and a transfer coating-of a compultion of comminuted carbon or other pigment or dye with wax and a fatty material such as petroleum jelly, is applied in a-molten condition to one side of the paper. The coating is solidified. and appears substantially as indicated at II in the drawing, upon and to some extent impregnating the paper stock II. The paper web is then run again through the same or a similar machine and a reverse or back coating 12 is applied.

The coating I2 is of chlorinated rubber or some mate'rial having substantially like properties. Preferably it is applied as a solution of 0111931 ated rubberof the range 5 to 20%v in mine], the percentage varying within approximately this range according to the degree of hardness of the ransfer coating on the particular-web andthe purposes intended to be served by the sheets cut therefrom. Any suitable P a lcizer may beincluded in the solution such as a vegetable oil or resin, approximately 5%, and'illlers and p flments or dyes may be included if desired. i

For the purpose of preventing curl and minimizing the objectionable slipping characteristic of the paper, it has been found that a solution of 5% chlorinated rubber in toluol is suitable. In cases where durability and sharpness of first writes are more important than manifolding properties it is preferred to use higher percentages of chlorinated rubber.

The solution may be applied according to any of the usual methods as, for example, by spraying, brushing or flowing, and the excess over 4 amount is removed by a, knife or other conventional gaging or levelling means. The solvent is then evaporated and the paper is subsequently rolled.

Chlorinated rubber as commercially produced in high chlorine content is of such specific gravity and density that its application to a thin web of carbon-faced paper adds materially to the weight, resistance and sensitiveness of the paper without unduly increasingits bulk. Furthermore the chlorination of the rubber so lowers its-viscosity that it can be made to runin almost water-thin solution to spread easily and evenly and impregnate the paper to some extent, yet it is highly cementitious and effective for the desired purposes. The high mobility of thechlo- 'rinated rubber in solution has a distinct imlportance to. this invention. The specific gravity of chlorinated rubber according to present proccases may be 1.5 andthe chlorine content may i -more"than its paper base, causing a carbon concave-curl. This type of curl has not been corrected by coatings. of gutta-percha which have V been attempted. 'The use of gutta-percha was intended for toughening the sheet.

According to a preferred method employed, the solution of chlorinated rubber in toluol is applied after the wax and carbon transfer-coating has been applied and solidified, for the reason that by firstapl lying and solidifying the wax coating the paper web is reenforced and held to a large extent against longitudinal stretching in the coating machine.

The final product derived from this invention isathin flexible sheet, soft but resilient and sensitive, stable under all room temperature conditions and provided with a backing which is a moisturesr'gsistant deposit .of chlorinated rubber from an evaporation of the solvent in a solution of the same and which consequently has substantial weight and density to prevent curling nf the. paper and add to its mechanical strength,

durability and manifolding properties. The backing of the sheet is unaffected by atmospheric changes. It is of excellent appearance with a slight lustre and it is just sumciently tacky to assist in maintaining the-sheet in position in the manifolding set.

What I'claim as new, is:-

1. A transfer web having on its face a transfer material and on its back a thin dense film of chlorinated rubber.

I which comprises applying a transfer coating to one sideof' a roll-fed paper web, applying chlorinated rubber in solution tothe other face of the web, removing excess of the solution, and evaporating the solvent.

5. A non-curling carbon-paper sheet having on its face a transfer material comprising comminuted carbon in wax and a fatty substance, and having chlorinated rubber on its back.

WALLACE PATTEN CQHOE. 

